Fuel delivery structure of an in-cylinder injection engine

Abstract

To provide a fuel delivery structure for a cylinder injection engine capable of approximately coping with increase of fuel injection pressure and a center injection system while suppressing cost increase.SOLUTION: A fuel delivery structure for the cylinder injection engine includes a cylinder head 2, a cylinder head cover 3, an injector 4 for injecting fuel into a combustion chamber of the cylinder head 2, and a fuel delivery pipe 5 for forcibly feeding and supplying the fuel to the injector 4, where the fuel is injected directly to the combustion chamber to cause combustion with spark ignition, the cylinder head cover 3 being made of metal, the injector 4 being arranged right above the cylinder head cover 3 and the combustion chamber, the fuel delivery pipe 5 being arranged to be connected to the injector 4 right above the injector 4, and fixed to the cylinder head cover 3.SELECTED DRAWING: Figure 6

Description

Technical Field

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[0001] The present invention relates to a spark ignition engine mounted on a vehicle, and particularly to a fuel delivery structure of an in-cylinder injection engine that directly injects fuel into a combustion chamber.

Background Art

[0002] Patent Document 1 describes an invention related to an internal combustion engine (a spark ignition engine such as a gasoline engine) including a plurality of injectors, a plurality of injector tubes into which the plurality of injectors are respectively inserted, a cylinder head provided with a plurality of spark plug tubes into which the plurality of spark plugs are respectively inserted, a head cover attached to the cylinder head, and a fuel delivery pipe that supplies fuel to the plurality of injectors. In the internal combustion engine described in this Patent Document 1, the injector holder is connected to the fuel delivery pipe in a first region between a first end portion and a first injector through-hole, and in a second region between a second end portion and a second injector through-hole. The first region and the second region are formed to have lower rigidity than a third region between the first injector through-hole and the second injector through-hole. Thereby, the stress generated in the injector holder due to the difference in thermal expansion between the fuel delivery pipe and the injector holder is alleviated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, the internal combustion engine described in Patent Document 1 is a direct injection engine that injects fuel directly into the combustion chamber using an injector, and is a so-called center-injection type direct injection engine in which the injector is positioned almost directly above the combustion chamber. Patent Document 1 also discloses the fuel delivery structure of that direct injection engine. Another example of such a direct injection engine and fuel delivery structure with the injector positioned directly above is shown in Figure 1. The direct injection engine 100 shown in Figure 1 is equipped with a resin cylinder head cover 101. The cylinder head cover 101 incorporates a cam carrier (or cam housing) 102 and is assembled to the cylinder head 103 together with the cam carrier 102. In the fuel delivery structure of this direct injection engine 100, four injectors 105 and a fuel delivery pipe 106 are attached to the upper surface of the cylinder head cover 101 via a metal injector holder 104. A high-pressure fuel pump 107 is connected to one end of the fuel delivery pipe 106, and fuel pumped from the fuel pump 107 is supplied to each injector 105 via the fuel delivery pipe 106.

[0005] In the direct injection engine 100 with a center injection system as described above, the injector 105 is positioned directly above the combustion chamber (not shown) of the cylinder head 103, between the intake valve (not shown) and the exhaust valve (not shown), and close to the spark plug (not shown). This is advantageous for forming a stratified mixture in the combustion chamber. Also, since the injector 105 is embedded inside the cylinder head, the operating noise of the injector 105 is less likely to be emitted to the outside. Furthermore, by adopting a resin cylinder head cover 101, the direct injection engine 100 can be made lighter and its sound insulation can be improved. On the other hand, in the fuel delivery structure of the direct injection engine 100, an aluminum alloy injector holder 104 and cam carrier 102 are used to compensate for the strength and rigidity of the resin cylinder head cover 101 in order to cope with the increased fuel injection pressure. As a result, compared to conventional direct injection engines that do not cope with high fuel injection pressure or the center injection system, the number of parts increases, which is a factor in cost increase.

[0006] This invention was conceived in response to the technical challenges described above, and aims to provide a fuel delivery structure for an in-cylinder injection engine that can appropriately accommodate high fuel injection pressure and a center injection system while suppressing or even reducing cost increases. [Means for solving the problem]

[0007] To achieve the above objective, this invention provides a fuel delivery structure for an in-cylinder injection engine, comprising a cylinder head, a cylinder head cover attached to the cylinder head and covering the upper surface of the cylinder head, an injector for injecting fuel into the combustion chamber of the cylinder head, and a fuel delivery pipe for pressurizing and supplying the fuel to the injector, wherein the fuel is injected directly into the combustion chamber and burned by spark ignition, the cylinder head cover is made of metal, the injector is positioned directly above the cylinder head cover and the combustion chamber, and the fuel delivery pipe is positioned directly above the injector The fuel delivery pipe is positioned above and has a main pipe section through which the fuel flows. Multiple boss sections for fastening to the cylinder head cover are provided on the main pipe section, protruding from both sides of the central axis of the main pipe section. The fuel delivery pipe is connected to the injector at the bottom and the boss sections are located in front of it.It is characterized by being fixed to the cylinder head cover.

[0008] Furthermore, in this invention The boss portion that protrudes to one side of the central axis of the main pipe and the boss portion that protrudes to the other side of the central axis of the main pipe are provided at diagonal bracing positions offset from each other in the direction of the central axis of the main pipe. stomach. [Effects of the Invention]

[0010] The engine targeted by this invention is a spark-ignition engine, such as a gasoline engine, and is a direct-injection engine that injects fuel directly into the combustion chamber using an injector. Furthermore, it is a so-called center-injection direct-injection engine in which the injector is positioned almost directly above the combustion chamber in the cylinder head. In the fuel delivery structure of the direct-injection engine of this invention, the fuel delivery pipe is positioned almost directly above the injector and connected to the injector. The fuel delivery pipe is attached and fixed to a metal cylinder head cover. Since a metal cylinder head cover has higher strength and rigidity than a resin cylinder head cover, parts such as injector holders, cam carriers, or cam housings that are used with a resin cylinder head cover can be eliminated. Therefore, even when high strength and rigidity are required to cope with high fuel injection pressure, the number of parts can be reduced compared to when a resin cylinder head cover is used, while appropriately ensuring the strength and rigidity to hold the center-injection injector.

[0011] Furthermore, in the fuel delivery structure of the in-cylinder injection engine of this invention, the fuel delivery pipe described above is fixed to the cylinder head cover at multiple points on both sides of the center line (main pipe section) in the longitudinal direction of the main pipe section extending in the direction of fuel flow. For example, it is fixed to the cylinder head cover at positions that are symmetrical left and right or up and down with respect to the center line of the main pipe section as the axis of symmetry. Alternatively, it is fixed to the cylinder head cover at positions that act as diagonal braces on both sides, left and right or up and down, with respect to the center line of the main pipe section. As a result, the fuel delivery pipe takes the form of a so-called fixed beam at both ends at the support portion with respect to the cylinder head cover, and vibration and displacement of the fuel delivery pipe can be suppressed compared to when the fuel delivery pipe is fixed on only one side (a so-called cantilever beam form). Consequently, the input of vibration load from the fuel delivery pipe to the injector and cylinder head cover can be reduced.

[0012] Therefore, according to the fuel delivery structure of the in-cylinder injection engine of this invention, it is possible to appropriately accommodate high fuel injection pressure and a center injection system while suppressing or even reducing cost increases. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a diagram illustrating the challenges of the conventional technology, and is a perspective view showing an example of a center-injection in-cylinder engine that employs a resin cylinder head cover and positions the injector almost directly above the combustion chamber of the cylinder head. [Figure 2] Figure 2 is a diagram illustrating the fuel delivery structure of the in-cylinder injection engine of this invention, and is a perspective view showing the cylinder head and a metal cylinder head cover of the in-cylinder injection engine. [Figure 3] Figure 3 is a diagram illustrating the fuel delivery structure of the in-cylinder injection engine of this invention, and is a perspective view showing the basic structure of the injector. [Figure 4]Figure 4 is a diagram illustrating the fuel delivery structure of the in-cylinder injection engine of this invention, and is a perspective view showing the basic structure of the fuel delivery pipe. [Figure 5] Figure 5 is a diagram illustrating the fuel delivery structure of the in-cylinder injection engine of this invention, and is a perspective view showing the fuel delivery pipe attached to a metal cylinder head cover. [Figure 6] Figure 6 is a diagram illustrating the fuel delivery structure of the in-cylinder injection engine of this invention, and is a top view showing the fuel delivery pipe attached to a metal cylinder head cover. [Modes for carrying out the invention]

[0014] Embodiments of this invention will be described with reference to the drawings. Note that the embodiments shown below are merely examples of how this invention can be implemented and do not limit the invention.

[0015] The direct injection engine in this embodiment of the invention is typically a spark-ignition engine that uses gasoline, or other fuels such as LPG, alcohol, or hydrogen, and is particularly a direct injection engine that injects fuel directly into the combustion chamber. Furthermore, the direct injection engine targeted in this embodiment of the invention is a so-called center-injection type direct injection engine, in which the fuel injector is positioned almost directly above the combustion chamber, as will be described later. As shown in Figure 2, the direct injection engine (hereinafter referred to as the engine) 1 in this embodiment of the invention is equipped with a metal cylinder head cover 3 that covers the upper surface of the cylinder head 2.

[0016] The cylinder head cover 3 is made of metal, such as an aluminum alloy or a magnesium alloy, for example, and is adopted for its high strength and rigidity compared to the resin-made cylinder head cover 101 in the direct injection engine 100 shown in FIG. 1 above. For example, in the example shown in FIG. 2, an aluminum alloy cylinder head cover 3 manufactured by an aluminum die-casting method is used. As shown in FIG. 2, an injector placement hole 3a for placing an injector 4 described later and a boss 3b for the fastening bolt for fixing a fuel delivery pipe 5 described later are formed in the cylinder head cover 3.

[0017] The injector placement hole 3a is a through hole formed at a predetermined position on the cylinder head cover 3 corresponding to the placement position of the injector 4 installed directly above a combustion chamber (not shown) formed in the cylinder head 2. In the example shown in FIG. 2, four injector placement holes 3a are provided at four positions corresponding to the four injectors 4 in the cylinder head cover 3, respectively.

[0018] The boss 3b for the fastening bolt is a boss-shaped part for attaching the fuel delivery pipe 5 to the cylinder head cover 3 by bolt fastening. A screw hole (not shown) for screwing in a fastening bolt (not shown) is formed in the boss 3b for the fastening bolt.

[0019] Also, the boss 3b for the fastening bolt is formed at a position corresponding to a boss 5c for the fastening bolt formed on the fuel delivery pipe 5 described later. That is, as will be described later, the boss 3b for the fastening bolt of the cylinder head cover 3 is provided at predetermined positions on both the left and right or top and bottom sides centered on the length direction of the main pipe part 5a of the fuel delivery pipe 5 (the fuel flow direction or supply direction in the fuel delivery pipe 5).

[0020] In addition, a spark plug placement hole 3c for fixing a spark plug (not shown) and a bolt hole 3d for attaching the cylinder head cover 3 to the cylinder head 2 by bolt fastening are formed in the cylinder head cover 3.

[0021] As described above, the resin cylinder head cover 101 as shown in FIG. 1 contributes to weight reduction and sound insulation improvement of the direct injection engine 100. However, the resin cylinder head cover 101 is disadvantageous in terms of strength and rigidity compared to a metal one. In the direct injection engine 100, for example, in order to cope with the high pressure of the fuel injection pressure, higher strength and rigidity are required for the cylinder head cover 101 compared to a conventional port injection type engine. Also, by adopting the center injection method as described above, the space for arranging the injector 105 on the cylinder head cover 101 becomes smaller, and as a result, the strength margin of the cylinder head cover (101) also becomes smaller. Therefore, in the direct injection engine 100 adopting the resin cylinder head cover 101, the injector holder 104 and the cam carrier 102 are used to compensate for the strength and rigidity of the resin cylinder head cover 101. As a result, the number of parts increases, which has been a factor in cost increase.

[0022] On the other hand, in the engine 1 according to the embodiment of the present invention, by adopting a metal cylinder head cover 3 with high strength and rigidity, parts such as the injector holder 104 and the cam carrier 102 can be eliminated compared to the resin cylinder head cover 101 as shown in FIG. 1. Therefore, it is possible to appropriately ensure the strength and rigidity of the cylinder head cover 3 in response to the high pressure of the fuel injection pressure and the special structure of the center injection method. And compared to the direct injection engine 100 adopting the resin cylinder head cover 101 as shown in FIG. 1, the number of parts can be reduced and cost reduction can be achieved.

[0023] And the fuel delivery structure of the in-cylinder injection engine according to the embodiment of the present invention includes an injector 4 and a fuel delivery pipe 5 as shown in FIGS. 3, 4, 5, and 6.

[0024] The injector 4 is a component that injects fuel into the combustion chamber of the cylinder head 2. As mentioned above, the engine 1 in this embodiment of the invention is a center-injection direct injection engine. Therefore, the injector 4 is positioned directly above the cylinder head cover 3 and the combustion chamber in the cylinder head 2 (directly above in the vertical direction).

[0025] As shown in Figure 3, the injector 4 is basically configured the same as a conventional "center injection type injector". That is, the main body (nozzle holder) 4a of the injector 4 is almost straight, and the injector mounting portion 5b of the fuel delivery pipe 5, which will be described later, is connected to its upper end 4b, and high-pressure fuel is supplied from the fuel delivery pipe 5. Inside the main body 4a of the injector 4, a valve mechanism (not shown) is formed from a solenoid (not shown) and a plunger (not shown). An injection nozzle portion 4c is formed at the tip (lower end) of the main body 4a, which directly injects fuel into the combustion chamber of the cylinder head 2.

[0026] In the example shown in Figure 3, the injector 4 is equipped with a nozzle holder clamp 4d. The nozzle holder clamp 4d tightens and connects the upper end portion 4b of the injector 4 to the injector mounting portion 5b of the fuel delivery pipe 5. At the same time, the nozzle holder clamp 4d is structured to press the injector 4 toward the cylinder head 2 by the elastic force of a spring (not shown). Therefore, for example, when starting the engine 1, where the fuel injection pressure is relatively low, the movement of the injector 4 due to combustion pressure can be suppressed, thereby improving the airtightness between the injector 4 and the cylinder head 2. In addition, vibrations and noise caused by the movement of the injector 4 can be reduced.

[0027] The fuel delivery pipe 5 supplies high-pressure fuel discharged from a fuel pump (not shown) to the injectors 4 under pressure. In the example shown in Figure 4, injectors 4 are installed in each of the four injector placement holes 3a formed in the cylinder head cover 3, and the fuel delivery pipe 5 distributes and supplies fuel to these four injectors 4.

[0028] As shown in Figure 4, the fuel delivery pipe 5 basically has the same configuration as a conventional "fuel delivery pipe for a direct injection engine." That is, it has a straight pipe section 5a with a predetermined length corresponding to the number of injectors 4 that supply fuel, and an injector mounting section 5b.

[0029] The main pipe section 5a is a tubular member connected to the fuel pump and extending in the direction of the main flow of fuel discharged from the fuel pump. Therefore, the length of this main pipe section 5a is in the direction of the main flow (or supply direction) of fuel in the fuel delivery pipe 5, DL.

[0030] The injector mounting section 5b is a boss-shaped part that branches off from the main pipe section 5a, and the injector 4 is connected and mounted thereto. As described above, the upper end portion 4b of the injector 4 is attached to the injector mounting section 5b using the nozzle holder clamp 4d.

[0031] In the example shown in Figure 4, the fuel pressure sensor 6 is mounted near the center of the main pipe section 5a of the fuel delivery pipe 5 in the longitudinal direction. The fuel pressure sensor 6 detects the pressure of the high-pressure fuel injected from the injector 4. In the example shown in Figure 6, which will be described later, the fuel pressure sensor 6 is mounted near the tip (the right end in Figure 6) of the main pipe section 5a of the fuel delivery pipe 5 in the longitudinal direction.

[0032] Furthermore, in this embodiment of the invention, the fuel delivery pipe 5 is positioned directly above the injector 4 (directly above in the vertical direction) and connected to the upper end 4b of the injector 4. In this state, the fuel delivery pipe 5 is fixed to the metal cylinder head cover 3.

[0033] As described above, a fastening bolt boss 5c is formed on the fuel delivery pipe 5 in order to fix the fuel delivery pipe 5 to the cylinder head cover 3. The fastening bolt boss 5c is a boss-shaped part for attaching the fuel delivery pipe 5 to the cylinder head cover 3 by bolt fastening. As shown in Figures 4 and 5, a bolt hole (through hole) 5d is formed on the fastening bolt boss 5c for inserting the fastening bolt 7.

[0034] The fastening bolt bosses 5c are provided at predetermined positions on the left and right or upper and lower sides of the fuel delivery pipe 5, centered on the fuel flow direction (or fuel supply direction) DL, along the length of the main pipe section 5a of the fuel delivery pipe 5, as shown in Figures 4, 5, and 6. In the fuel delivery structure of the in-cylinder injection engine according to this embodiment of the invention, for example, the fastening bolt bosses 5c are formed at positions that are symmetrical to the left and right or upper and lower sides, with respect to the fuel flow direction DL in the fuel delivery pipe 5 as the axis of symmetry. In the example shown in Figure 6, the fastening bolt bosses 5c are formed at the diagonal bracing positions on both the upper and lower sides of the fuel delivery pipe 5, centered on the fuel flow direction DL. In other words, the fuel delivery pipe 5 is fixed to the cylinder head cover 3 at the diagonal bracing positions on both the left and right or upper and lower sides, centered on the center line (i.e., flow direction DL) in the length of the main pipe section 5a.

[0035] Therefore, the fuel delivery pipe 5 has a so-called fixed-bore configuration at the support portion with the cylinder head cover 3, which suppresses vibration and displacement of the fuel delivery pipe 5 compared to the conventional case where the fuel delivery pipe 5 is fixed on only one side (a so-called cantilever configuration). Consequently, the input of vibration load from the fuel delivery pipe 5 to the injector 4 and cylinder head cover 3 can be reduced.

[0036] As described above, in the fuel delivery structure for a direct injection engine in this embodiment of the invention, the fuel delivery pipe 5 is positioned almost directly above the injector 4 and connected to the injector 4, targeting a so-called center injection type direct injection engine 1. The fuel delivery pipe 5 is then attached and fixed to a metal cylinder head cover 3. The metal cylinder head cover 3 has higher strength and rigidity compared to the "resin cylinder head cover" shown in the prior art. Therefore, parts such as "injector holders," "cam carriers," or "cam housings" that are used together with the "resin cylinder head cover" can be eliminated. Thus, even when high strength and rigidity are required to cope with high fuel injection pressure, the number of parts can be reduced compared to when a "resin cylinder head cover" is used, while appropriately ensuring the strength and rigidity to hold the center injection type injector 4.

[0037] Therefore, according to the fuel delivery structure for an in-cylinder injection engine in this embodiment of the present invention, it is possible to appropriately accommodate high fuel injection pressure and a center injection system while suppressing or reducing cost increases. [Explanation of Symbols]

[0038] 1. In-cylinder injection engine (direct injection engine with center injection system) 2 Cylinder heads 3 Cylinder head cover 3a Injector placement hole (formed in the cylinder head cover) 3b Bosses for fastening bolts (formed on the cylinder head cover) 3c (Spark plug mounting hole formed in the cylinder head cover) 3D (bolt holes formed in the cylinder head cover) 4 Injectors 4a (Injector) main body (nozzle holder) 4b Upper end (of the injector) 4c (Injector) Nozzle 4d (Injector) Nozzle Holder Clamp 5. Fuel delivery pipe 5a Main section (of the fuel delivery pipe) 5b Injector mounting section (of the fuel delivery pipe) 5c (Boss for fastening bolts on fuel delivery pipes) 5d (Fuel delivery pipe) Bolt hole (through hole) 6. Fuel pressure sensor 7 Fastening bolts 100 [Conventional Technology] Direct injection engine (center injection system) 101 [Prior Art] Resin cylinder head cover 102 [Prior Art] Cam carrier (or cam housing) 103 [Prior Art] Cylinder Head 104 [Prior Art] Injector Holder 105 [Prior Art] Injector 106 [Prior Art] Fuel Delivery Pipe 107 [Prior Art] Fuel Pump DL fuel flow direction (supply direction)

Claims

1. A fuel delivery structure for an in-cylinder injection engine, comprising a cylinder head, a cylinder head cover attached to the cylinder head and covering the upper surface of the cylinder head, an injector for injecting fuel into the combustion chamber of the cylinder head, and a fuel delivery pipe for supplying the fuel to the injector under pressure, wherein the fuel is injected directly into the combustion chamber and burned by spark ignition, The cylinder head cover is made of metal. The injector is positioned directly above the cylinder head cover and the combustion chamber. The fuel delivery pipe is positioned directly above the injector. The fuel delivery pipe has a main pipe section through which the fuel flows, Multiple bosses for fastening to the cylinder head cover are provided on the main pipe, protruding from both sides of the central axis of the main pipe, The fuel delivery pipe is fixed to the cylinder head cover via the boss portion, with the injector connected to its lower part. A fuel delivery structure for an in-cylinder injection engine characterized by the following.

2. A fuel delivery structure for an in-cylinder injection engine according to claim 1, The boss portion protruding to one side of the central axis of the main pipe and the boss portion protruding to the other side of the central axis of the main pipe are positioned at diagonal bracing positions offset from each other in the direction of the central axis of the main pipe. A fuel delivery structure for an in-cylinder injection engine characterized by the following.

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